Lormetazepam--plasma concentrations in volunteers following sublingual and oral dosing.

The plasma profile of lormetazepam has been determined in sixteen clinically healthy, adult male volunteers following 1 mg lormetazepam, administered either sublingually or by the oral route. Absorption of lormetazepam was found to be rapid following both sublingual and oral administration. While a trend was observed towards a more rapid rate of absorption after sublingual dosing, statistically, there was no significant difference (p greater than 0.05) between the speed with which lormetazepam was absorbed following sublingual and oral dosing. After absorption, plasma lormetazepam levels rapidly reached mean (+/- s.d.) peak concentrations of 4.9 +/- 0.9 ng/ml and 5.2 +/- 1.7 ng/ml for the sublingual and oral routes, respectively, there being no significant difference (p greater than 0.05) between these values. Likewise, there was no significant difference (p greater than 0.05) in the times at which peak plasma levels were attained in the two groups. Furthermore, measurement of the area under each plasma concentration-time curve showed that the bioavailability of lormetazepam was the same for the two routes of administration. Elimination of lormetazepam followed a similar pattern following sublingual and oral dosing, the mean terminal half-lives being 13.0 h and 13.8 h, respectively. The findings in the present study clearly indicate that the plasma profiles of lormetazepam attained on sublingual and oral dosing are similar, indeed the pharmacokinetic characteristics of this drug appear identical being independent of its route of administration.